Two Kenyan marathon runners have been banned after positive tests for banned substances following suspensions for three other marathoners from the east African nation last month.
Athletics Kenya secretary general David Okeyo told Reuters on Thursday that Salome Jerono Biwott and Jynocel Basweti Onyancha had both been suspended for two years.
Last month marathon runners Wilson Erupe Loyanae and Nixon Kiplagat Cherutich were banned for two years while Moses Kiptoo Kurgat was suspended for a year.
"The number is growing and we are not happy about the statistics. We only hope that the culprits remain at a manageable level and that the (doping) issue is not as widespread as previous reports have indicated," Okeyo said.
Last week German freelance journalist Hajo Seppelt told Reuters an underground television investigation aired before last year's London Olympics had convinced him there was a widespread doping problem in the country which, along with Ethiopia, dominates distance running.